Active waveshaper for deep penetrating oil-field charges

ABSTRACT

A shaped charge having a liner, a shaped charge case, high explosive between the ilner and the case, and an active wave shaping element that is made of an energetic material that reacts at a rate different from the high explosive. The wave shaping element is disposed in the high explosive between an apex of the liner and base of the shaped charge case. Example materials of the wave shaping element include HMX, RDX, PBX types, PETN, HNS, TATB, and combinations thereof.

BACKGROUND

1. Field of Invention

The present invention relates to ballistics devices used in oil and gas production. More specifically, the present invention relates to a shaped charge having a wave shaping element having an energetic material.

2. Description of Prior Art

Hydrocarbon producing wellbores typically intersect multiple zones within subterranean formations. Perforating systems are often used for perforating hydraulic passages through walls of the wellbores into one or more of the zones thereby hydraulically communicating the perforated zones to the wellbore. Wellbores are usually completed by coaxially inserting a pipe or casing into the wellbore where it is then cemented in place by pumping cement into the annular space between the wellbore and the casing. The cement forms a flow barrier hydraulically isolating the zones from one another in the annular space.

The perforating systems typically include a gun body that houses a number of shaped charges. FIG. 1 illustrates a prior art example of a shaped charge 10. Each shaped charge 10 generally include a housing 12, a liner 14, and high explosive 16. Traditionally some of the high explosives that have been used are HMX, RDX, PBX types, and PETN. The housing 12 usually has an open end and a cylindrically shaped open space or cavity 17 therein in which the explosive 16 and liner 14 are provided. Liners 14 are typically metal particles that are molded into thin walled, hollow, and conically shaped members having a rounded apex and open at the base. The liner 14 is disposed into the open space 17 of the housing 12, apex side first, with the high explosive 16 between the liner 14 and housing 12. Detonating the high explosive 16 forms detonation waves 18 that transmit through the high explosive 16 and collapse and invert the liner 14, converting the liner 14 into an elongated metal jet that is ejected from the shaped charge housing 12. The jet exits the gun body and penetrates the well casing and the surrounding geologic formations. The jet properties depend on the shape of the charge case 12 and liner 14, released energy, as well as the mass and composition of the liner 14. Generally the high explosive 16 is detonated by exploding a booster charge 20 shown adjacent the high explosive 16, where the booster charge explosion is initiated by an associated detonation cord 22.

Various efforts have been made to modify the performance of shaped charges. Barriers and voids have been placed within the explosive material to modify the detonation wave shape collapsing the liner. Wave shaping techniques have involved positioning the high explosive between the detonator cord and the liner. For example, a spoiler was positioned within the liner cavity to modify the perforating jet shape. Other efforts have been made to modify perforating jet performance by changing the liner shape, thickness, or configuration.

SUMMARY OF THE INVENTION

The present disclosure describes examples of a shaped charge and methods of perforating a wellbore. In one example embodiment, disclosed herein is a shaped charge that includes a high explosive having a speed of detonation and a liner adjacent the high explosive. A wave shaping element is included with the shaped charge that is made of an energetic material, where the energetic material has a speed of reaction less than the speed of detonation of the high explosive. The wave shaping element is disposed in a path of a detonation wave, which is between a location of initiation of the detonation wave and the liner. Thus when the detonation wave is generated by detonation of the high explosive and propagates through the wave shaping element, the detonation wave is shaped by the wave shaping element. In one example embodiment, the detonation wave upstream of the wave shaping element is more divergent than when the detonation wave is downstream of the wave shaping element. Optionally, the wave shaping element is made up of HMX, RDX, PBX types, PETN, HNS, TATB, or combinations thereof. A shaped charge case may be included with the shaped charge, where the shaped charge case has a cavity formed through one of its ends for placing the high explosive and liner. Also, a booster charge may optionally be disposed in an end of the shaped charge case opposite the end having the cavity. In an example, the liner has a generally conical shape with a rounded apex facing the booster charge, and wherein the wave shaping element is disposed in a space between the apex and the booster charge. The wave shaping element may have a lenticular cross section and can be generally coaxial with an axis of the shaped charge. The high explosive may be made up of a material such as HMX, RDX, PBX types, PETN, HNS, TATB, or combinations thereof.

Also included herein is a method of perforating a wellbore. In one example the method involves providing a shaped charge having a shaped charge liner and with high explosive adjacent the shaped charge liner. The method also includes providing a wave shaping element in the high explosive. The wave shaping element of this example is made up of an energetic material whose rate of reaction differs from the rate the high explosive reacts. The shaped charge is then disposed in a wellbore and is initiated to form a detonation wave for collapsing the shaped charge liner. Optionally, the wave shaping element diverges less downstream than when upstream of the wave shaping element. Alternatively, initiating detonation of the high explosive can include generating a detonation wave in a detonating cord and transferring the detonation wave from the detonating cord to the high explosive. The method can further optionally include disposing the high explosive, shaped charge liner, and wave shaping element in a shaped charge case to define a shaped charge. The steps of providing can be repeated multiple times to obtain multiple shaped charges that can be disposed into a perforating gun having a detonation cord.

A perforating system is also described herein that includes a cylindrical perforating gun body having shaped charges. The shaped charges include a shaped charge case having a cavity with walls and a bottom, a shaped charge liner in the cavity, high explosive between the shaped charge liner and the walls and bottom of the cavity, and a wave shaping element in the cavity between an apex of the shaped charge liner and bottom of the cavity. The wave shaping element includes a material that reacts at a rate different from that at which the high explosive reacts. In one optional embodiment, the material of the wave shaping element includes HMX, RDX, PBX types, PETN, HNS, TATB, or combinations thereof. Further optionally included is a detonating cord extending lengthwise through the gun body and disposed adjacent an end of the shaped charge case having a booster charge. In one example, the wave shaping element is coated with a fluorocarbon based polymer. The apex may optionally extend into the wave shaping element. Alternatively, the wave shaping element is spaced apart from the apex.

BRIEF DESCRIPTION OF DRAWINGS

Some of the features and benefits of the present invention having been stated, others will become apparent as the description proceeds when taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a side sectional view of a prior art example of a shaped charge.

FIG. 2 is a side sectional view of an example embodiment of a shaped charge in accordance with the present invention.

FIG. 3 is a partial side sectional view of an example embodiment of perforating a wellbore using the shaped charge of FIG. 2 in accordance with the present invention.

FIGS. 4A and 4B are side sectional views of example embodiments of the shaped charge of FIG. 2 in accordance with the present invention.

While the invention will be described in connection with the preferred embodiments, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications, and equivalents, as may be included within the spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF INVENTION

The method and system of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings in which embodiments are shown. The method and system of the present disclosure may be in many different forms and should not be construed as limited to the illustrated embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey its scope to those skilled in the art. Like numbers refer to like elements throughout.

It is to be further understood that the scope of the present disclosure is not limited to the exact details of construction, operation, exact materials, or embodiments shown and described, as modifications and equivalents will be apparent to one skilled in the art. In the drawings and specification, there have been disclosed illustrative embodiments and, although specific terms are employed, they are used in a generic and descriptive sense only and not for the purpose of limitation. Accordingly, the improvements herein described are therefore to be limited only by the scope of the appended claims.

An example embodiment of a shaped charge 30 is shown in a side sectional view in FIG. 2 that is made up of a shaped charge case 32 having a cavity 33 formed through one end of the shaped charge case 32. A conically-shaped liner 34 is shown inserted within the cavity 33 that has a rounded apex directed towards a base or bottom of the cavity 33. In the example of FIG. 2, the liner 34 is substantially coaxial with an axis Ax of the shaped charge 30. High explosive 36 is shown disposed between the liner 34 and walls and base of the cavity 33. Optionally included with the high explosive 36 is a binder 37 that in one example embodiment can be used for shaping the high explosive 36 within the shaped charge case 32. The binder 37 may be a wax-based material or may be a polychlorotrifluoroethylene, as well as other fluorocarbon-based polymers.

Provided in the space between the apex of the liner 34 and base of the cavity 33 is a wave shaping element 38. The wave shaping element 38 of FIG. 2 has a generally lenticular cross section having a major axis and a minor axis; wherein the minor axis is generally coaxial with the axis Ax. In the example embodiment of FIG. 2, the wave shaping element 38 includes a coating 39 on its outer surface that in an example embodiment includes a fluorocarbon-based polymer. The material making up the wave shaping element 38 is energetic and having a rate of reaction that differs from a rate of reaction of the high explosive 36. Example materials for the wave shaping element 38 include HMX, RDX, PBX types, PETN, HNS, TATB, and combinations thereof.

The shaped charge 30 of FIG. 2 further includes a booster charge 40 shown provided in the bottom end of the shaped charge case 32 and opposite the opening to the cavity 33. The booster charge 40 includes a material that reacts more readily than the high explosive 36. In one example embodiment the booster charge 40 is made up of a primary explosive and the high explosive 36 is made up of a secondary explosive; wherein the primary explosive detonates in response to a stimulus that would generally not initiate detonation within the high explosive 36. Detonation of the booster charge 40 though is capable of detonating the high explosive 36.

A detonating cord 42 is shown set adjacent an end of the booster charge 40 opposite the high explosive 36 and is provided for initiating explosion or detonation within the booster charge 40. An example detonation wave 44 is illustrated within FIG. 2, that in an example depict how detonation of the high explosive 36 can initiate from the booster charge 40, propagate along a path running substantially parallel with the axis Ax, and ultimately exit the shaped charge 30.

In an example embodiment, the presence of the wave shaping element 38, as illustrated, alters the shape of the detonation wave 44 to a less diverging configuration. For example, the detonation wave 44 upstream of the wave shaping element 38 is shown having a radius that is less than a radius of the detonation wave 44 downstream of the wave shaping element 38. As discussed above, the material of the wave shaping element 38 as disclosed herein is energetic and explodes and/or detonates in response to detonation of the high explosive 36. Detonation or explosion of the wave shaping element 38 may be caused directly by the detonation wave 44. An advantage of a wave shaping element 38 that is active, rather than passive is that attenuation of the detonation wave 44 through the active wave shaping element 38 is less than attenuation through wave shaping elements formed from a nonreactive material.

In an example embodiment, the wave shaping element 38 provides a lensing effect of reshaping the configuration of the detonation wave 44. Although the detonation wave 44 propagating downstream of the wave shaping element 38 is shown as having a non-linear wave front, the wave front may optionally be substantially linear and oriented generally perpendicular with the direction of the axis Ax. Other configurations exist wherein the detonation wave 44 has a wave front inverted from that of FIG. 2; that is having a radius with an origin on a side of the detonation wave 44 opposite that of the booster charge 40.

A faster collapsing liner 34 and thus deeper penetration is one advantage of shaping the wave front of the detonation wave 44. An advantage of combining the binder 37 with the high explosive 36 is that the high explosive 36 may be conformed into a desired shape, and having a precise contour and dimensions. The binder 37 also increases repeatability of forming high explosive 36 into a desired shape with precise dimensions and contour. Increased precision allows for more symmetrically shaped high explosives that in turn form more coherent and straighter jets that those generated by less symmetrically formed high explosives. Because incoherency of jet formation is exacerbated with increasing jet velocity, embodiments combining the wave shaping element 38 with precisely configured high explosive 36 substantially symmetric about the axis Ax, provides for the higher velocity detonation wave 44 and jet formed by the inverting liner 34 that is on and not offset from the axis Ax.

Referring now to FIG. 3, an example embodiment of a perforating system 45 is shown in a partial sectional view and disposed within a borehole 46. In the example of FIG. 3, the shaped charge 30 of FIG. 2 is provided with an elongated and substantially cylindrical perforating gun 48 that is attached to other perforating guns to define a perforating string. Shaped charges 30 are provided in the perforating guns 48. An example of the step of perforating is shown in FIG. 3 wherein jets 49 are shown being discharged from the shaped charges 30 within the perforating guns 48 and that form perforations 50 into a formation 52 that surrounds the borehole 46. An example advantage of using the wave shaping element 38 is that the perforations 50 may penetrate deeper and straighter within the formation 52 than shaped charges not having a wave shaping element. Moreover, the wave shaping element 38 as disclosed herein may form perforations 50 that are deeper than those formed by other shaped charges having a passive wave shaping element.

Further in the example of FIG. 3, a wireline 54 is included that can be used for deploying the string of perforating guns 48 within the borehole 46. The wireline 54 may also be used for directing a signal to the perforating guns 48 that causes detonation of the shaped charges 30. The wireline 54 is shown passing through a wellhead assembly 56 that is mounted on an upper end of the bore hole 46. Control of the wireline 54, and optionally the signals through the wire line 54, is maintained via a surface truck 58 shown set on the surface and above the bore hole opening. In the perforating system 45, an initiator 60 is shown on an upper end that couples with the detonating cord 42, that as discussed above, initiates explosion or detonation within the booster charge 40 (FIG. 2).

FIGS. 4A and 4B provide alternate embodiments of the shaped charge 30 of FIG. 2. Specifically as illustrated in FIG. 4A, a shaped charge 30A is provided wherein the wave shaping element 38 is not intersected by the apex of the liner 34, instead the wave shaping element 38 is positioned to be in contact with and adjacent the apex of the liner 34. In another optional embodiment, a shaped charge 30B is shown in sectional view in FIG. 4B wherein the wave shaping element 38 is spaced rearward of the apex of the liner 34, thereby leaving a space between the wave shaping element 38 and apex of the liner 34. In both embodiments of FIGS. 4A and 4B, the resulting detonation waves 44 take on a less diverging configuration downstream of the wave shaping element 38 than upstream so that the collapsing of the liner 34 occurs at a rate that is faster than that would occur without the strategically located wave shaping element 38. As such, higher energy jets may be produced for providing deeper penetrations within hydrocarbon-producing formations.

The present invention described herein, therefore, is well adapted to carry out the objects and attain the ends and advantages mentioned, as well as others inherent therein. While a presently preferred embodiment of the invention has been given for purposes of disclosure, numerous changes exist in the details of procedures for accomplishing the desired results. For example, coiled tubing may be used in place of the wireline. These and other similar modifications will readily suggest themselves to those skilled in the art, and are intended to be encompassed within the spirit of the present invention disclosed herein and the scope of the appended claims. 

1. A shaped charge for use in perforating a wellbore comprising: a shaped charge case configured for use in a perforating gun; a high explosive in the shaped charge case having a speed of detonation; a liner adjacent the high explosive in the shaped charge case: a wave shaping element comprising an energetic material having a speed of reaction less than the speed of detonation and disposed in a path, of a detonation wave that is between a location of initiation of the detonation wave and the liner, so that when the detonation wave is generated by detonation of the high explosive, the detonation wave Is shaped by the wave shaping element.
 2. The shaped charge of claim 1, wherein the detonation wave upstream of the wave shaping element, is more divergent than when the detonation wave is downstream, of the wave shaping element.
 3. The shaped charge of claim 1, wherein the wave shaping element comprises a material selected from the list consisting of HMX, RDX, PBX types, PETN, HNS, TATB, and combinations thereof.
 4. The shaped charge of claim 1, further comprising a cavity formed through an end of the shaped charge case, wherein the high explosive and liner is disposed in the cavity.
 5. The shaped charge of claim 4, further comprising a booster charge in an end of the shaped charge case opposite the end having the cavity, wherein the liner has a generally conical shape with a rounded apex facing the booster charge, and wherein the wave shaping element is disposed in a space between the apex and the booster charge.
 6. The shaped charge of claim 1, wherein the wave shaping element has a lenticular cross section and is generally coaxial with an axis of the shaped charge.
 7. The shaped charge of claim 1, wherein the high explosive comprises a material selected from the list consisting of HMX, RDX, PBX types, PETN, HNS, TATB, and combinations thereof.
 8. A method of perforating a wellbore comprising: a. providing a shaped charge having a shaped charge liner, high explosive adjacent the shaped charge liner, and a wave shaping element in the high explosive that comprises an energetic material that has a rate of reaction, that differs from a rate of reaction of the high explosive; b. disposing the shaped charge in a wellbore; and c. initiating detonation of tie high explosive to form a detonation wave for collapsing the shaped charge liner.
 9. The method of claim 8, wherein the detonation wave downstream of the wave shaping element diverges less than when upstream of the wave shaping element.
 10. The method of claim 8, wherein the step of initiating detonation of the high explosive comprises generating a detonation wave in a detonating cord, and transferring the detonation wave from the detonating cord to the high explosive.
 11. The method of claim 8, further comprising disposing the high explosive, shaped charge liner, and wave shaping element in a shaped charge ease to define a shaped charge.
 12. The method of claim 8, further comprising repeating step (a) multiple times to provide multiple shaped charges, disposing the multiple shaped charges into a perforating gun having a detonation cord.
 13. A perforating system comprising: a cylindrical perforating gun body; shaped charges in the gun body comprising a shaped charge case having a cavity with, walls and a bottom, a shaped charge liner in the cavity, high explosive between the shaped charge liner and the walls and bottom of the cavity, and a wave shaping element in the cavity between an apex of the shaped charge liner and bottom of the cavity and that comprises a material that reacts at a rate different from that at which the high explosive reacts.
 14. The perforating system of claim 13, wherein the material of the wave shaping element comprises HMX, RDX, PBX types, PETN, HNS, TATB, and combinations thereof.
 15. The perforating system of claim 13, further comprising a detonating cord extending lengthwise through the gun body and disposed adjacent an end of the shaped charge case having a booster charge.
 16. The perforating system of claim 13, wherein the wave shaping element is coated with a fluorocarbon based polymer.
 17. The perforating system of claim 13, wherein the apex extends into the wave shaping element.
 18. The perforating system of claim 13, wherein the wave shaping element is spaced apart from the apex. 